Devices and methods for suppression of tinnitus

ABSTRACT

Methods and devices for treating tinnitus in human or animal subjects wherein the subject is caused to perceive a tinnitus suppressing sound which fully or partially suppresses the subject&#39;s tinnitus. In some embodiments of this method, the subject selects a sound that he or she perceives to be the same as the tinnitus and that sound (or a similar sound that is complementary to the subject&#39;s perceived tinnitus) is then used as the tinnitus suppressing sound. In other embodiments, the tinnitus suppressing may be a sound that has previously been determined to suppress tinnitus in a substantial number of subjects.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/746,171, filed on Jan. 20, 2011, now U.S. Pat. No. 8,357,102, whichis a National Stage Entry of PCT Application No. PCT/US08/85652 filedDec. 5, 2008, and also claims priority to U.S. Provisional PatentApplication No. 60/992,638 filed Dec. 5, 2007, the entire disclosuredisclosures of which is are expressly incorporated herein by reference.

STATEMENT REGARDING GOVERNMENT SUPPORT

This invention was made with Government support under Grant No.DC-002267, awarded by the National Institutes of Health. The Governmenthas certain may have rights in this invention.

FIELD OF THE INVENTION

The present invention relates generally to biomedical devices andmethods and more particularly to devices and methods usable for thetreatment of tinnitus.

BACKGROUND OF THE INVENTION

Tinnitus is the perception of sound in the absence of correspondingexternal sounds. Tinnitus may be caused by injury, infection or therepeated bombast of loud sound, and can appear in one or both ears.Although known for its high-pitched ringing, tinnitus is an internalnoise that varies in its pitch and frequency. The sound perceived mayrange from a quiet background noise to a signal loud enough to drown outall outside sounds.

Tinnitus affects approximately 50 million Americans or about 15% of thegeneral population. There is no effective treatment to amelioratetinnitus. The prior art has included devices and methods that attempt tomask tinnitus.

General Hearing and several others manufacture an earpiece that cangenerate sound. The masking methods work well for people who suffer mildforms of tinnitus but don't work for people who suffer from loudtinnitus because to mask the tinnitus, the external sound has to belouder than the tinnitus.

Some treatments, such as drugs, surgery, psychotherapy and masking,exist, but none are consistently effective and may have significant sideeffects. Here we propose to use sound to suppress tinnitus. Differentfrom previous masking methods, which use an external sound that istypically louder than the tinnitus and has similar pitch quality to thetinnitus, we propose to use optimized sounds that may be softer and havedifferent pitch qualities than the tinnitus. Another significantdifference between previous masking devices and the present suppressingmethod is that the masking effect is instantaneous, while the presentsuppressing method usually takes time to develop and decay. The soundcan be delivered either acoustically via an audio device (e.g., MP3players, iPod® devices, or other ear devices) or electrically via atemporary or permanent implant.

In particular, various medications have been used to treat tinnitus,which are aimed at the disease or its co-morbidities. Tinnitus is oftenassociated with anxiety and depression. Whether the condition causespsychological distress or whether tinnitus is more prevalent in peoplewith psychological disorders is under debate. It has been suggested thattricyclic antidepressants treat the underlying psychological problemsrather than the tinnitus directly. Some studies have demonstratedsignificant decrease in tinnitus intensity with the administration ofintravenous (IV) lidocaine but have not reproduced the effect with oralanalogues such as tocainide. IV administration of lidocaine is not apractical method due to its short half-life and serious side effects.Other agents, such as carbamazepine, alprazolam, baclofen, betahistine,and cinnarizine have also been studied as possible tinnitus treatments,with inconsistent results. Selective serotonin reuptake inhibitors haveshown no benefit or a slight benefit in placebo-controlled studies.

Tinnitus masking devices of the prior art deliver a continuous low-levelnoise or tone to the ear that results in camouflaging of the tinnitus.Use of the device has been shown to reduce tinnitus severity. TheNeuromonics tinnitus treatment is a new method of acoustic stimulationin combination with a structured program of counselling. The deviceoutput is a broadband stimulus that is constructed for each individual'shearing profile. Three clinical trials reported general improvement inquality of life of patients using this treatment. Hearing aids alsogrant partial or total relief from tinnitus by amplifying external soundstimuli thereby decreasing the awareness of the presence of tinnitus.Hearing aids are usually tried as first line treatment in patients withtinnitus in the presence of hearing loss. Hearing aids can also be usedin combination with sound generators that increase the rate of success.

In the end of 1980s the neurophysiological model of tinnitus wasproposed which then elicited the development of a new therapeuticapproach called tinnitus retraining therapy (TRT). TRT consists ofcounselling along with delivery of a low-level, constant white noise tothe affected ear(s) of a patient. The sound usually results inhabituation of the patient's auditory system to the tinnitus therebydecreasing the patient's awareness of their condition. The rate ofsuccess varies between different patients. TRT requires one-to-two yearsof therapy for effective management of tinnitus.

Cochlear implantation has been found to be effective in reducingtinnitus in 28% to 79% of patients who have associated bilateral severesensorineural hearing loss in previous studies. Exacerbation of tinnitusis reported in 9% of patients after cochlear implantation. Success withcochlear implants in decreasing tinnitus has led to other forms ofelectric stimulation, including transtympanic stimulation of thecochlea, vestibulocochlear nerve stimulation, and transcranial magneticstimulation of the auditory cortex. Recent studies have shown that 1 outof 3 cochlear implant users and 5 out of 11 (45%) transtympanic subjectsshowed substantial or total tinnitus relief while stimulated by highrate pulse trains. More than that, the external perception was eitherpresented subthreshold or diminished to below threshold within a shortperiod of time. This is the ideal situation for tinnitus suffers sinceboth the tinnitus and external stimulus are not perceived as a result.In a review of the literature, unilateral cochlear implant use wassuggested to be associated with decline of contralateral tinnitus in 67%of patients. The effect of a cochlear implant is demonstrated to be dueto masking of tinnitus by surrounding sounds that are newly perceived orfrom electrical stimulation of the auditory nerve. The mechanismsunderlying the complexity of tinnitus are unclear, and a cure for thiscondition remains elusive. The prevailing theories generally point toeither a central or peripheral source of subjective tinnitus, defined assound perceivable only to the patient without a clear organic cause. Thereality most likely involves a combination of both, with peripheralinjuries and pathology causing functional and architectural changes inthe central nervous system.

United States Patent Application Publication 2007/0203536 (Hochmair etal.) describes cochlear implant devices as well as other implantabledevices usable to deliver tinnitus treatment. The entire disclosure ofUnited States Patent Application Publication 2007/0203536 is expresslyincorporated herein by reference.

U.S. Pat. No. 7,347,827 (Choy) describes monofrequency tinnitus patienttreatment apparatus and process wherein phase cancellation effects arepurported to be achieved by utilizing an externally generated soundwhich is subjectively selected by the monofrequency tinnitus patient tomatch in both tone and loudness his or her tinnitus sound. Thissubjectively selected externally generated sound wave which matches intone and loudness the patient's tinnitus sound, is either (i)sequentially phase shifted through a plurality of phase shift sequencesteps totaling at least 180 degrees or (ii) alternatively is directlyphase shifted in essentially a single step motion into a 180 degree,out-of-phase reciprocal, canceling relationship with the patientdetermined tinnitus tone. The sequential steps of the phase shifted toneor the directly phase shifted tone are applied to the tinnitus patientto effect cancellation or diminishment of the patient's tinnitus. Theentire disclosure of U.S. Pat. No. 7,347,827 (Choy) is expresslyincorporated herein by reference.

Phase cancellation techniques, such as that described in U.S. Pat. No.7,347,827 (Choy) may not be optimally effective in treating tinnitus.Most tinnitus is of high frequency (>1000 Hz) although somelow-frequency tinnitus cases do exist. However, even if a person'stinnitus is low frequency, the phase canceling techniques may beineffective or less than optimal because the perceived tinnitus sound isa neural impulse not an acoustic sound and cannot be physically orexternally cancelled by phase inversion. Physiologically all sounds willbe half-wave rectified in the cochlea and become digital-like pulses(called action potentials) in the nervous system. An out-of-phaseexternal sound will add, rather than cancel, the internally-generatedtinnitus.

Tinnitus occurs in the setting of sensorineural hearing loss in themajority of patients, thus the postulate that tinnitus originatesperipherally in the cochlea. Noise damage causes molecular changes tostructural proteins in stereocilia and the cuticular plate. Cytoplasmiccalcium levels increase dramatically in response to sound, potentiallydisrupting normal hair cell function. Progressive insult results incomplete destruction of hair cells in certain regions of the basilarmembrane. Aberrant auditory signals occur around areas of hair cellloss, an edge effect that results in the perception of sound.Furthermore, auditory nerve fibers are spontaneously active duringquiet, resulting in neurotransmitter release. Loss of the spontaneousactivity can lead to abnormal central auditory activity, which could beperceived as sound. Lack of sound input and edge effects as a cause oftinnitus could explain the reduction of tinnitus commonly seen followingcochlear implantation. Tinnitus suppression by electrical stimulation inhearing and deaf patients has been shown in a relatively recent study.

On the other hand, not all patients with hearing loss experiencetinnitus, and not all tinnitus patients have hearing loss. Sectioning ofthe auditory nerve can result in tinnitus, suggesting a centraletiology. Positron emission tomography (PET) imaging of patients withtinnitus shows unilateral neural activity in Brodmann areas 21,22, andpossibly 42. These effects were decreased with lidocaine administration,a known suppressor of tinnitus. Sounds caused bilateral activityregardless of which ear was stimulated. Patients who experiencedtinnitus in response to facial movement showed unilateral changes incerebral blood flow. Another study using single photon emission computedtomography (SPECT) imaging during tinnitus showed a 16% increase insignal in the right auditory cortex and a 5% increase in the left,whereas noise caused bilateral change. The effect was eliminated bylidocaine administration. This difference in the activation patternsupports a theory of central generation of tinnitus.

This interpretation is consistent with animal models of tinnitus showingchanges in spontaneous activity of the dorsal cochlear nucleus (DCN)following noise or cisplatin exposure. This hyperactivity persistsfollowing ablation of the damaged cochlea, suggesting that while aperipheral injury may stimulate a change in the DCN, the centralhyperactivity is independent of peripheral input.

Tinnitus has been separated in three categories depending on severityand if hearing loss is present. Category 0 is characterized by thetinnitus having a low impact on the person's life. Categories 1 and 2are used to describe tinnitus with a high impact on life with Category 2indicating the presence of subjective hearing loss that accompanies thetinnitus. For our studies this convention was followed but a secondparameter based on loudness was defined. The loudness parameter wasdetermined by each subject as Low, Moderate or High. On a 10-point scalewith 1 being the lowest sound (threshold) and 10 being the upper limitof loudness, Low is 0 to 3, Moderate is 3 to 6, and High is 6 to 10.Careful measures were taken to ensure each subject understands they areranking loudness and not annoyance.

FIG. 1 of this patent application is a graphic representation oftinnitus severity classification and the typical tinnitus patientpopulation. Patients within category 0 are least likely to seek tinnitustreatment. Category 1 and 2 patients with low levels of loudness arelikely to be helped by TRT. It has been shown that TRT helps inrelaxation for a majority of patients (72.5%) but benefits a muchsmaller percentage with respect to their ability to work (25.5%) andsleep (47%). At present, category 1 and 2 patients with high levels ofloudness are often left without effective treatment.

There remains a need in the art for the development of new devices andmethods for the treatment of tinnitus.

SUMMARY OF THE INVENTION

The present invention provides methods and devices for suppressingtinnitus rather than merely masking it.

In accordance with one aspect of the present invention, there isprovided a method for treating tinnitus in a human or animal subjectcomprising the step of causing the subject to perceive a tinnitussuppressing sound which fully or partially suppresses the subject'stinnitus. In some embodiments of this method, the subject selects asound that he or she perceives to be the same as the tinnitus and thatsound (or a similar sound that is complementary to the subject'sperceived tinnitus) is then used as the tinnitus suppressing sound. Inother embodiments of this method, the tinnitus suppressing may be asound that has previously been determined to suppress tinnitus in asubstantial number of subjects. In some embodiments of this method, thetinnitus suppressing sound is perceived by the subject as being softerthan the tinnitus, thereby lowering the subject's perceived soundenvironment. In some embodiments of this method, at least one variableof the tinnitus suppressing sound is varied to optimize the degree towhich the subject's tinnitus is suppressed. The tinnitus suppressingsound may be delivered as acoustic sound or as electrical stimulus, suchas electrical stimuli delivered via a cochlear implant.

Further in accordance with the present invention, there is provided adevice for suppressing tinnitus in a human or animal subject, suchdevice comprising an apparatus which causes the subject to perceive atinnitus suppressing sound that results in suppression of the subject'stinnitus. In some embodiments of this device, the device may compriseapparatus that enables the subject to hear a number of sounds and toselect a particular sound that he or she perceives to be the same as thetinnitus and the device may thereafter play the selected sound oranother sound that is complementary to the selected sound as thetinnitus suppressing sound. In other embodiments of this device, thetinnitus suppressing sound may be a sound that has previously beendetermined to suppress tinnitus in a substantial number of subjects. Insome embodiments of this device, the tinnitus suppressing sound will beplayed such that it is perceived by the subject as being softer than thetinnitus, thereby lowering the subject's perceived sound environment. Insome embodiments of this device, at least one variable of the tinnitussuppressing sound may be varied to optimize the degree to which thesubject's tinnitus is suppressed. This may be accomplished using abiofeedback processor or other suitable apparatus. The device maydeliver the tinnitus suppressing sound may be delivered as acousticsound (e.g., a sound playing device and speaker(s) or earpiece(s)) or aselectrical stimulus (e.g., an electrical signal generating or deliveringdevice which delivers the signal to the subject by way of an inserted orimplanted electrode, electrode array or cochlear implant).

Further aspects, details, objects, elements, steps and advantages of thepresent invention will be understood by those of skill in the art uponreading of the detailed description and examples set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic representation of tinnitus severity classificationsand a typical tinnitus patient population.

FIG. 2 is a flow diagram showing an example of a method of the presentinvention.

FIG. 2A is a graphic illustration showing differences between tinnitusmasking and tinnitus suppression.

FIG. 3 is a composite graph of loudness level vs. time duration whichestimates loudness for both tinnitus and the external sound as afunction of the sound duration in each of two subjects treated inExample 1 below.

FIG. 4 is a composite graph of loudness level vs. time duration whichestimates the total loudness of the tinnitus and the tinnitussuppressing or masking sounds in order to compare the effectiveness ofmasking versus suppression in each of two subjects treated in Example 1below.

FIG. 5 is a graph of loudness estimates vs. time showing the monopolarapical condition and demonstrating that while the stimulus producedtotal adaptation, no effect was seen on the tinnitus in one of thesubjects treated in Example 1 below.

FIG. 6 shows that low-rate stimulation (100 Hz) produced little or noadaptation but could totally suppress his tinnitus.

DETAILED DESCRIPTION AND EXAMPLES

The following detailed description and the accompanying drawings towhich it refers are intended to describe some, but not necessarily all,examples or embodiments of the invention. The described embodiments areto be considered in all respects only as illustrative and notrestrictive. The contents of this detailed description and theaccompanying drawings do not limit the scope of the invention in anyway.

When tinnitus is masked, as in the prior art, the tinnitus sound iscovered with a masking sound, such as a white noise or band passednoise, that is equal to or greater in volume than the tinnitus sound.Thus, when tinnitus is masked, the subject's sound environment is thesame or louder than listening to their tinnitus alone since the maskingsound must be at least equal in volume to the tinnitus sound in order tocompletely cover the tinnitus sound. If the masker is presented quieterthan the tinnitus, a case known as partial masking occurs. As the nameindicates, this is when the tinnitus is partially covered so it appearslower in volume but the presence of the partial masker makes the totalsound environment approximately the same. The present inventionsuppresses tinnitus by providing to the subject a tinnitus suppressionsound (which may be an external acoustic sound or electrical cochlear orneural stimulation that corresponds to the desired tinnitus suppressionsound). The tinnitus suppression sound may be lower in volume than thetinnitus and will substantially or completely eliminate the subject'sperception of the tinnitus. As a result, the subject hears only thelower volume suppression sound. Since this suppression sound may besofter than the tinnitus, the total sound environment may be decreasedby use of the present invention.

FIG. 2 shows a flow diagram of one example of a tinnitus suppressingmethod of the present invention. In this method, a matched tone mayoptionally be obtained for loudness and pitch of the subjectivetinnitus. Such tinnitus matching tone is obtained by presenting anexternal tone to the subject who is instructed to adjust the tone'samplitude and frequency to match the perceived tinnitus' loudness andpitch. The external tone is optimally presented to the ear contralateralto the tinnitus ear if the tinnitus is unilateral, or to the ear withthe least amount of hearing loss if the tinnitus is bilateral.Additionally, the tinnitus matching tone is the most accurately obtainedby a double-bracketing procedure in which the amplitude of the externaltone is first presented to be much softer than the perceived tinnitusloudness and then to be much louder; the range of the softer and louderamplitudes is reduced until the external tone is just noticeably softeror louder than the perceived tinnitus loudness. The average of the justnoticeable softer and louder amplitudes for the external tone is thematched tinnitus loudness. Once the matched tinnitus loudness isobtained, the frequency of the external tone is varied to be much lowerand higher than the perceived tinnitus pitch. Similarly, the range ofthe frequencies is reduced until the external tone is just noticeablylower or higher than the perceived tinnitus pitch. The average of thenoticeable lower and higher frequencies for the external tone is thematched tinnitus pitch.

Second, a tinnitus suppressing sound (which may have the matchedloudness and pitch) is selected for use with the subject. This may beaccomplished in any suitable way. For example, the subject may listen toa series of sounds (e.g., through headphones) and select the particularsound that he or she perceives to be the same as or highly similar tothe perceived tinnitus. That selected sound may then be used as thetinnitus suppressing sound. Another example would be to utilize apre-selected tinnitus suppressing sound that has been determined byprior experience to suppress tinnitus in a substantial number ofsubjects. The tinnitus suppressing sound may be amplitude or frequencymodulated sound.

After the tinnitus suppressing sound has been selected, it is deliveredto the subject in a series of treatments or continuously to effectsuppression of the subject's tinnitus. As described more fully below,the tinnitus suppressing sound may delivered in the form of acousticsound (e.g., via speakers, earphones, headset, earbuds, ear canalinserted speakers, etc.) or as electrical stimulation to the cochlea,auditory nerve or appropriate area of the brain. Non-limiting examplesof cochlear implants and implantable electrodes that may be used todeliver tinnitus suppressing treatments of the present invention aredescribed in the above-incorporated United States Patent ApplicationPublication 2007/0203536 (Hochmair et al.).

Optionally, the tinnitus suppressing sound or at least one component orvariable of the tinnitus suppressing sound may be varied to optimize thedegree to which the subject's tinnitus is suppressed.

Also, optionally, the loudness of the tinnitus suppressing sound may beadjusted to be softer than the tinnitus, thereby allowing the subject toavoid being subjected to an unnecessarily high perceived soundenvironment. The tinnitus suppressing sound may be delivered as acousticsound or as electrical stimulus, such as electrical stimuli deliveredvia a cochlear implant.

Also, optionally, when it is desired to terminate the tinnitussuppressing sound (such as at the end of a particular treatment period)the sound may be gradually turned off, producing an offset ramp thatdecreases the loudness of the tinnitus suppressing sound to eliminate asudden rebound of the tinnitus.

FIG. 2A shows graphically the differences between tinnitus masking andtinnitus suppression. With total masking, the tinnitus will not beaudible, but the masker will be louder than the tinnitus. For partialmasking, the masker is softer than the tinnitus, the perception of thetinnitus is reduced, but the overall level of sound (masker plustinnitus) is similar to the tinnitus alone. For suppression, a sound ispresented that is softer than the tinnitus but completely eliminates theperception of the tinnitus. The overall level will be less than thetinnitus alone.

The present invention includes a sound delivery device and method tosuppress tinnitus. The device is any device that is usable to deliversound that has complementary characteristics to the tinnitus. Such soundmay be delivered acoustically via an audio device (e.g., stereo or monosound emitting device with speaker(s) (e.g., speakers, earpiece(s),headphone(s), etc.) or electrically via an electrode or electrode array,such as a needle electrode, ear implant, cochlear implant, etc. Thesound can be static or dynamic, including pure tones, click trains,amplitude-modulated and frequency-modulated sounds as well as speech andmusic. The sound will typically include a long offset ramp to reduce oreliminate the rebound of tinnitus after the suppression. A rebound isdefined as an increase in the perceived level of tinnitus following asound that masks or suppresses it.

Further in accordance with the present invention, there are provideddevices and methods which provide to a subject's brain sound input thatis complementary to tinnitus, thereby suppressing the tinnitus. Oneadvantage of the present invention is that it may provide an externalsound that doesn't have to be as loud as the perceived tinnitus sound,and in fact, can be much softer than the perceived tinnitus sound orbarely audible, but can nonetheless suppress tinnitus. The search forsuch suppressor sound can be optimized with a biofeedback processor.

One objective of the present invention is to deliver an effective andlow-cost means of completely suppressing tinnitus via custom andpatterned acoustic or electric stimulation. Applicant's approach is toidentify these customized and patterned acoustic and electric stimuli ina selected group of patients whose tinnitus cannot be controlled bycurrent conventional methods. Although the mechanisms are unclear, it ishypothesized that a unique external stimulus, acoustic or electric,exists to suppress tinnitus for each patient. Based on Applicant's data,this unique stimulus is able to suppress tinnitus effectively and tooperate in a totally different mechanism than masking. For thetraditional masker to be effective, it needs to have similar temporaland spectral properties to the tinnitus. For the present suppressor, ittends to have complementary properties to the tinnitus, e.g., alow-pitch sound can be used to suppress high-pitched tinnitus.

A further objective of the present invention is to provide additionalmeans for studying and elucidating the mechanisms underlying tinnitusand tinnitus suppression as well as to identify an objective marker oftinnitus.

EXAMPLE 1

In this example, two adults with unilateral continuously high-leveltinnitus were identified and tested. Subject AS1 has had tinnitus for2.5 years, a moderate loss of 50 dB at 8 kHz, ranks the tinnitus to be 7of 10 loud, and matches the tinnitus to an 8-kHz, 70-dB SPL pure tone inthe contralateral ear. AS1 is thus a Category 1 unilateral High (seeFIG. 1). Subject AS2 has had tinnitus for 1.5 years, a hearing loss of25-40 dB at 4-8 kHz, ranks the tinnitus to be 5 of 10, and matches thetinnitus to a 7-kHz, 69-dB SPL pure tone in the contralateral ear. AS2is a Category 1 unilateral Moderate.

FIG. 3 shows loudness estimate for both tinnitus and the external soundas a function of the sound duration. An 8-kHz tone presented at 80 dBSPL can totally mask AS1's tinnitus (upper left panel). An 8-kHz tonepresented at 60 dB SPL can partially mask the tinnitus from 7 to 4 loud(middle left panel). However, the same tone presented 60 dB SPL (2loud), if amplitude-modulated by an 80-Hz sinusoid, can totally suppressthe tinnitus (bottom left panel). Subject AS2 showed a similar patternexcept for significant residual suppression lasting up to 30 minutes.

FIG. 4 estimates the total loudness of the tinnitus and the sound inorder to compare the effectiveness of masking versus suppression. Thedashed line represents the initial level of tinnitus and is used to showif the overall percept is higher or lower. In total masking, theperception is higher during the presentation of the stimulus due to thefact that the sound needed to be louder than the tinnitus. For partialmasking, the overall level is roughly equal to the tinnitus during thepresentation. Subject AS2 had lower sound after offset due toextraordinary residual inhibition. With suppression, the overall levelis decreased during the presentation of the sound. The bottom line isthat suppression can be a viable treatment to reduce the subject'soverall perceived loudness of the tinnitus and the external sound. Inother words, we can replace tinnitus with a much softer, and hopefullymuch more pleasant, external sound. Ideally we would like to find anexternal stimulus that is sub-threshold or can totally adapt while stilleffective in totally suppressing tinnitus. At present, the 80-Hzamplitude modulated sound represents the best option for AS1 who haspurchased an Ipod and downloaded an 8-hour version of this modulatedsound to relieve his tinnitus on a daily basis.

In this example, a 47-year-old male subject, who has had unilateralhearing loss (right ear), imbalance and debilitating tinnitus since June2004. He received a Clarion HiRes 90K cochlear implant device (in hisright ear to control tinnitus. The subject had reported no relief fromthe HiRes Sequential strategy loaded in the Auria processor. Tinnitusquality was measured by matching between the tinnitus in the right earand the sound delivered to his good ear (normal hearing in the leftear), and mainly consisted of band-passed noise from 500-8000 Hz at70-90 dB SPL with intermittent higher frequency components. He is aCategory 2 unilateral High.

To test the effect seen in prior art, this subject was stimulated with5000 Hz pulse trains. Apical and basal as well as monopolar and bipolarconfigurations were tested. Pulse widths were 53.9 us/phase. Monopolarstimulation is delivered using one intracochlear electrode and onereference electrode (Clarion HiRes 90K cochlear implant, AdvancedBionics, Valencia, Calif.) located on the internal receiver of thecochlear implant device, which indicates that the current will have abroad stimulation area. Bipolar stimulation is delivered using twoadjacent intracochlear electrodes, which indicates that the region ofstimulation will be much more restricted. A research interface andsoftware (Bionic Ear Data Collection System—BEDCS, Advance BionicsCorp., Valencia, Calif.) were used to generate and deliver the electricstimulation.

FIG. 5 shows the monopolar apical condition and demonstrates that whilethe stimulus produced total adaptation, no effect was seen on thetinnitus in this subject. Loudness adaptation was measured using thesuccessive loudness estimation every 30 seconds (See Tang, Liu and ZengJARO 2006). Similar results were seen with all high rate stimulation.

On the other hand, FIG. 6 shows that low-rate stimulation (100 Hz)produced little or no adaptation but could totally suppress histinnitus. A 40% increase (“rebound”) above baseline tinnitus wasobserved at the offset of the electric stimulus and lasted for about 1minute.

Applicants have also found that the effective suppressor requiredcritical rates (20-130 Hz), critical places (the most apical severalelectrodes), and critical level (had to be at least 2 of 10 loud). Pulsewidth for the effective low rate stimuli were 107.8 us/phase. Objectivemeasures in both spontaneous and event-related evoked potentials alsoshowed a difference related to the presence and absence of tinnitus.

Applicants have since produced a similar sound using his clinical speechprocessor that also resulted in effective tinnitus suppression. Thepatient has used this modified processor on a daily basis to relieve histinnitus. As a result, this patient has stopped taking medication forhis tinnitus.

These data show a fundamental difference between suppression andmasking. Ideally the promising results can be generalized to a widerange of patients.

Test Stimuli

For acoustic suppression, sound was generated digitally using theTucker-Davis Technologies (TDT) system III (Tucker-Davis Technologies,Inc., Alachua, Fla.) and delivered through headphones. A 16-bit D/Aconverter will be used with a 44,100 Hz sampling rate. A 2.5-ms rampwill be applied to all stimuli to avoid spectral splatter. Stimuli willinclude pure tones from 20 Hz to 10 kHz, sinusoidal amplitude modulated(SAM) tones with center frequencies 100 Hz to 10 kHz and modulationfrequencies from 0.5 Hz to a 25% of the center frequency, and band passnoises at different cutoff frequencies. Levels from barely audible tosufficiently loud to completely mask will be used.

Subjects with cochlear implants will have their internal receiverconnected directly to the research interface bypassing their externalspeech processor. Electric stimulation will be delivered either as pulsetrains or as electric sinusoids where possible (e.g., Bionic Ear DataCollection System—BEDCS, Advanced Bionics, Valencia, Calif.).Stimulation rates from 10 to 10,000 pps, all electrodes from apex tobase, and envelope modulation rates from 0.5 Hz to 25% of the carrierpulse rate will be tested. Levels consistent with the acoustic stimuliwill be used. Stimuli are verified through an oscilloscope to confirmaccuracy before delivery to the subjects.

Test Procedure

If the subject has normal or some degree of residual hearing, tinnituswill be matched to external stimuli in terms of the loudness and pitch.This is done by presenting a low pitch (100 Hz) or a high pitch (10000Hz) to the contralateral ear in unilateral tinnitus or the ear withsofter tinnitus in bilateral tinnitus. The subject is asked to identifythe pitch as higher or as lower than their tinnitus. The frequency isadjusted until it is deemed a match or very close. If the sound qualityis too different from a pure tone to warrant a match, the subject isasked to describe the sound and another match using broad or narrow bandnoise or an amplitude or frequency modulation will be attempted. Levelis then adjusted to match the loudness between tinnitus and the externalstimulus. Should accurate match be needed, the PI has developed and useda double-staircase adaptive procedure (Zeng and Turner 1991).

The subjects are instructed to be familiar with a 1-10 ranking scalewith 1 being threshold, 6 being most comfortable level (MCL), and 10being the upper limit of loudness (ULL). Subjects report the level oftheir tinnitus prior to any acoustic or electric presentation. Thestimuli are presented and the subject is asked to report on the loudnessof the presented sound and the level of their tinnitus at 20-secondintervals. Subjects will be instructed to try to make independentreports of loudness that are not biases by previous responses. If thesubject cannot identify their tinnitus in the presence of the stimulus,a value of zero will be assigned. Sounds will be presented for 3 to 6minutes. Reports are made for 1 to 4 minutes after stimulus offset tomeasure the presence and duration of residual inhibition.

Potential Problems and Alternative Strategies

In at least some subjects, a rebound increase in tinnitus can occurafter the offset of an acoustic or electric tinnitus suppressing soundin this invention. In some cases, the rebound can persist for hours whena suppressor is used upwards of 8 hours. One method to alleviate therebound is to produce an offset ramp of approximately one minute in thesuppressor. The offset ramp gradually decreases the amplitude of thetinnitus suppressing sound over a 1 minute or longer period.

The above-described event-related evoked potentials can be used toderive a tinnitus “signature” that can then be used to objectivelyidentify the presence and absence of tinnitus. Applicants have foundthat N100 may be such a signature. Identification of an objectivetinnitus signature is critical to the assessment of the effectiveness oftinnitus treatment as well as the diagnosis of tinnitus in children andthe development of an animal tinnitus model.

It is to be appreciated that the invention has been described hereabovewith reference to certain examples or embodiments of the invention butthat various additions, deletions, alterations and modifications may bemade to those examples and embodiments without departing from theintended spirit and scope of the invention. For example, any element orattribute of one embodiment or example may be incorporated into or usedwith another embodiment or example, unless otherwise specified of if todo so would render the embodiment or example unsuitable for its intendeduse. Also, where the steps of a method or process have been described orlisted in a particular order, the order of such steps may be changedunless otherwise specified or unless doing so would render the method orprocess unworkable for its intended purpose. All reasonable additions,deletions, modifications and alterations are to be consideredequivalents of the described examples and embodiments and are to beincluded within the scope of the following claims.

What is claimed is:
 1. A method for generating a modulated sound fortreating tinnitus in a human subject, comprising the steps of: adjustinga frequency of a presented sound as a function of feedback from a humansubject to generate an adjusted sound comprising at least a matchedpitch of the subject's tinnitus; generating a sound comprising thematched pitch; and amplitude modulating or frequency modulating thegenerated sound to generate a modulated sound, wherein the modulatedsound has an adjustable intensity lower than the subject's perceivedloudness of the tinnitus.
 2. The method of claim 1, wherein theadjusting step comprises adjusting the frequency of the presented soundincluding reducing a range of frequencies until the matched pitch isreached, wherein said range of frequencies varies from lesser than togreater than a perceived pitch.
 3. The method of claim 1, wherein theadjusting step comprises adjusting an amplitude of the presented sound.4. The method of claim 3, wherein the adjusting step comprises adjustingthe amplitude of the presented sound including reducing a range ofamplitudes until a perceived loudness is reached, wherein said range ofamplitudes varies from zero to greater than a perceived loudness.
 5. Themethod of claim 1, further comprising applying the modulated sound tothe subject, thereby suppressing the tinnitus of the subject.
 6. Themethod of claim 5, further comprising receiving additional feedback fromthe subject after applying the modulated sound and, as a function of theadditional feedback, adjusting an intensity of the modulated soundwithin a range from zero to less than a perceived loudness.
 7. Themethod of claim 1, further comprising adding an offset ramp to themodulated sound.
 8. The method of claim 1, further comprising storingthe modulated sound to a portable audio device.
 9. The method of claim1, wherein the modulating step comprises modulating the generated soundwith a sinusoid to generate the modulated sound.
 10. The method of claim1, wherein the generated sound has an amplitude and wherein themodulating step comprises modulating the amplitude of the generatedsound to generate an amplitude-modulated sound.
 11. The method of claim1, wherein the generated sound has a frequency and wherein themodulating step comprises modulating the frequency of the generatedsound to generate a frequency-modulated sound.
 12. A device forgenerating a modulated sound for treating tinnitus in a human subject,said device comprising: a processor executing instructions for:adjusting a frequency of a sound presented to a human subject as afunction of feedback received from a subject to generate an adjustedsound comprising a matched pitch of the subject's tinnitus; generating asound comprising the matched pitch; and amplitude modulating orfrequency modulating the generated sound to generate a modulated sound,wherein the modulated sound has an adjustable intensity lower than thesubject's perceived loudness of the tinnitus.
 13. The device of claim12, the processor further executing instructions for applying themodulated sound to the subject via an audio interface, therebysuppressing the tinnitus of the subject.
 14. The device of claim 12,wherein the processor further executes instructions for: presenting thesound to the subject via an audio interface; and receiving the feedbackfrom the subject via an input interface.
 15. The device of claim 14,further comprising: the audio interface for presenting the sound to thesubject; and the input interface for receiving the feedback from thesubject.
 16. The device of claim 15, the processor further executinginstructions for applying the modulated sound to the subject via theaudio interface, thereby suppressing the tinnitus of the subject. 17.The device of claim 12, wherein said adjusting further includesadjusting an intensity of the presented sound.
 18. The device of claim12, the processor further executing instructions for: receivingadditional feedback from the subject after applying the modulated sound;and, as a function of the additional feedback, adjusting an intensity ofthe modulated sound within a range from zero to less than the perceivedloudness.
 19. The device of claim 12, wherein the processor furtherexecutes instructions for transferring the modulated sound to a portableaudio device.
 20. The device of claim 12, wherein the device includes aportable audio device.
 21. The device of claim 20, wherein the portableaudio device comprises an acoustic ear device, an earpiece, a headset ora speaker for producing a sound as a function of the modulated sound.22. The device of claim 12, wherein the generated sound is modulatedwith a sinusoid to generate the modulated sound.
 23. The device of claim12, wherein the generated sound has an amplitude and wherein themodulating step comprises modulating the amplitude of the generatedsound to generate an amplitude-modulated sound.
 24. The device of claim12, wherein the generated sound has a frequency and wherein themodulating step comprises modulating the frequency of the generatedsound to generate a frequency-modulated sound.